IPv6 Questions

My setup is Toastman's latest R2 build with USB and VPN on an Asus RT-N16:

I have the HE IPv6 tunnel setup properly in Tomato. Now, I know that IPv4 is running alongside IPv6. If I JUST want to run IPv6 (internally, of course), is it possible, and how? Will Tomato act as a 6to4 relay or will IPv4 traffic get routed with IPv6 to HE? If it gets routed to HE, will HE perform the relay?
Any other considerations I should think about?